A seat belt pretensioner is a device that is used with seat belt webbing to help protect a vehicle occupant upon the occurrence of a vehicle crash. When the pretensioner is actuated, it imparts tension to the webbing to help ensure that the webbing restrains movement of the vehicle occupant.
An inflatable device also may be used to help protect the vehicle occupant. One particular type of inflatable vehicle occupant protection device is known as an air bag. Other inflatable vehicle occupant protection devices include, for example, inflatable seat belts, inflatable knee bolsters, inflatable headliners or side curtains, and knee bolsters operated by inflatable air bags. Each of these devices is inflated by fluid received from a source which is actuated upon the occurrence of a vehicle crash.
A pretensioner and an inflatable vehicle occupant protection device are typically included in a system which further includes a crash sensor and a controller. The crash sensor senses the occurrence and the severity of a vehicle crash. The crash severity may be great enough for both the pretensioner and the inflatable device to be used for protection of the vehicle occupant. If so, the controller responds by providing the pretensioner with an electrical actuation signal, and also by providing the source of inflation fluid with an electrical actuation signal.